OldHW4 - hiarker (srh959) – oldhomework 04 – Turner –...

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Unformatted text preview: hiarker (srh959) – oldhomework 04 – Turner – (58220) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points The velocity v ( t ) of some particle is plotted as a function of time on the graph below. The scale on the horizontal axis is 7 s per division and on the vertical axis 1 m / s per division. Initially, the particle is at x = 51 m. 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 v ( t ) time ( × 7 s) velocity( × 1m / s) What is the position x of the particle at time t = 28 s? Correct answer: 121 m. Explanation: Looking at the v ( t ) plot we see that over time t = 4 (7 s) = 28 s, the particle’s velocity decreases from the initial v = 4 (1 m / s) = 4 m / s to final v f = 1 (1 m / s) = 1 m / s . The v ( t ) line is straight, which indicates constant deceleration rate, so the average velocity is given by ¯ v = v + v f 2 = 4 m / s + 1 m / s 2 = 2 . 5 m / s , the particle’s displacement is Δ x = t · ¯ v = (28 s) (2 . 5 m / s) = 70 m , and its final position x = x + Δ x = 51 m + 70 m = 121 m . 002 (part 2 of 2) 10.0 points What is the particle’s acceleration? Correct answer:- . 107143 m / s 2 . Explanation: The average acceleration of the particle is ¯ a = Δ v Δ t = v f- v t = 1 m / s- 4 m / s 28 s =- . 107143 m Since the v ( t ) line is straight, the acceleration is constant, so a = ¯ a =- . 107143 m / s 2 . 003 (part 1 of 2) 10.0 points A speeder passes a parked police car at 34.9 m/s. Instantaneously, the police car starts from rest with a uniform acceleration of 2.42 m/s 2 . a) How much time pases before the speeder is overtaken by the police car? Correct answer: 28 . 843 s. Explanation: Basic Concepts: For the speeder, Δ x s = v s Δ t For the policeman, v i = 0 m/s, so the equa- tion simplifies to Δ x p = 1 2 a p (Δ t ) 2 Let : v s = 34 . 9 m / s v i,p = 0 m / s a p = 2 . 42 m / s 2 ....
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This note was uploaded on 04/23/2010 for the course PHY 303K taught by Professor Nui during the Spring '09 term at University of Texas-Tyler.

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OldHW4 - hiarker (srh959) – oldhomework 04 – Turner –...

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